Polarization dependence of resonant Raman scattering from vertically aligned single-walled carbon nanotube films (original) (raw)
Related papers
Resonance Raman Spectra of Carbon Nanotubes by Cross-Polarized Light
Physical Review Letters, 2003
Resonance Raman studies on single wall carbon nanotubes (SWNTs) show that resonance with cross polarized light, i.e., with the E ;1 van Hove singularities in the joint density of states needs to be taken into account when analyzing the Raman and optical absorption spectra from isolated SWNTs. This study is performed by analyzing the polarization, laser energy, and diameter dependence of two Raman features, the tangential modes (G band) and a second-order mode (G 0 band), at the isolated SWNT level.
Resonant Raman effect in single-wall carbon nanotubes
A resonant Raman study of single-wall carbon nanotubes (SWNT) using several laser lines between 0.94 and 3.05 eV is presented. A detailed lineshape analysis shows that the bands associated with the nanotube radial breathing mode are composed of a sum of individual peaks whose relative intensities depend strongly on the laser energy, in agreement with prior work. On the other hand, the shape of the Raman bands associated with the tangential C-C stretching motions in the 1500-1600 cm 21 range does not depend significantly on the laser energy for laser excitation energies in the ranges 0.94-1.59 eV and 2.41-3.05 eV. However, new C -C stretching modes are observed in the spectra collected using laser excitations with energies close to 1.9 eV. The new results are discussed in terms of the difference between the 1D electronic density of states for the semiconducting and metallic carbon nanotubes.
Coupling of Raman Radial Breathing Modes in Double-Wall Carbon Nanotubes and Bundles of Nanotubes
The Journal of Physical Chemistry B, 2009
Measurements of the radial breathing modes from Raman Spectroscopy have been most useful in characterizing the diameters of single-wall carbon nanotubes (SWNT), where there is a simple monotonic relationship between frequency and diameter. Similar correlations have also been used to predict sizes for double and multiple wall nanotubes and for bundles of SWNT. However this can lead to significant errors because the relationship between frequencies and diameter is much more complicated for DWNT. This is because of couplings between the vibrations of various walls. To provide guidance in such assignments we used the GraFF atomistic force field to predict the in-phase and counter-phase radial breathing modes (RBMs) of double wall carbon nanotubes (DWNTs) over a broad range of inner and outer diameters and chiralities. We then developed an analytical model to describe the RBMs of dispersed DWNTs. This enables the inner and outer shell diameters to be extracted from pairs of RBM peaks. We find that nanotubes bundles show significant dependent peak broadening and shifting compared to dispersed nanotubes. For bundles of SWNT and DWNT, the relationships are much more complicated.
Raman studies on 0.4 nm diameter single wall carbon nanotubes
Chemical Physics Letters, 2002
We performed polarized Raman scattering studies on 0.4 nm diameter single wall carbon nanotubes (SWNTs) grown inside the pores of zeolite crystals, using several dierent laser lines (1:92 6 E laser 6 2:71 eV). The strong diameterselective resonant behavior of typical SWNTs (1 < d t < 3 nm) is not observed. The Raman spectra instead show a complicated pro®le that re¯ects the sp 2 carbons phonon density of states superimposed on the characteristic SWNT Raman features. We show that the behavior of typical SWNTs can be used qualitatively to analyze the radial breathing mode (RBM), G-band and D-band spectra of the 0.4 nm diameter SWNTs. Ó
Diameter-Selective Raman Scattering from Vibrational Modes in Carbon Nanotubes
Science, 1997
Single wall carbon nanotubes (SWNTs) that are found as close-packed arrays in crystalline ropes have been studied by using Raman scattering techniques with laser excitation wavelengths in the range from 514.5 to 1320 nanometers. Numerous Raman peaks were observed and identified with vibrational modes of armchair symmetry (n, n) SWNTs. The Raman spectra are in good agreement with lattice dynamics calculations based on CC force constants used to fit the two-dimensional, experimental phonon dispersion of a single graphene sheet. Calculated intensities from a nonresonant, bond polarizability model optimized for sp 2 carbon are also in qualitative agreement with the Raman data, although a resonant Raman scattering process is also taking place. This resonance results from the one-dimensional quantum confinement of the electrons in the nanotube.
Journal of Chemical Sciences, 2003
The paper discusses the design of a low cost Raman spectrometer. Singlewalled nanotubes (SWNT) have been studied to demonstrate the reach of such a system. We observe both the radial-breathing mode (RBM) and the tangential mode from the SWNT. The tube diameters of the SWNT used in these experiments have been determined using RBM to be predominantly 1⋅4 and 1⋅6 nm. These are consistent with the TEM images taken of the same sample. The new method of producing SWNT using Ni-Y catalyst in electric-arc discharge method produces nanotubes with very small dispersion in diameter and high yields. The chirality of the SWNT can be deduced from their radial breathing modes, and it suggests that they are metallic in nature.
Raman Scattering of Carbon Nanotubes
NATO Science Series II: Mathematics, Physics and Chemistry
The present state of Raman scattering from carbon nanotubes is reviewed. In the first part of the presentation the basic concepts of Raman scattering are elucidated with particular emphasis on resonance scattering. The classical and the quantum-mechanical description are presented and the basic experimental instrumentation and procedures are described. Special Raman techniques are discussed. Eventually, a short review on the electronic structure of single wall carbon nanotubes (SWCNTs) is given. The second part of the presentation deals with Raman scattering from SWCNTs. A group theoretical analysis and the origin of the basic Raman lines are described. For the radial breathing mode the observed quantum oscillations and the unusual strong Raman cross section are discussed. For the G line the resonance behavior and the response to doping is demonstrated and the calculated dependence of the line frequency on the tube diameter is summarized. For the D-line and for the G'-line the dispersion is demonstrated and its origin from a triple resonance is described. Finally, the response from pristine and doped peapods is elucidated. In the third part most recent results are reported from Raman spectroscopy of double wall carbon nanotubes (DWCNTs). The unusual narrow lines with widths down to 0.4 cm-1 indicate clean room conditions for the growth process of the inner tubes. (n,m) assignment to them and high curvature effects are discussed. Results for DWCNTs where the inner tubes are highly 13 C substituted are reported with respect to Raman and NMR spectroscopy. Eventually, it is demonstrated that the RBM Raman lines of the inner tubes cluster into groups of up to 14 lines where each member of the cluster represents a pair of inner-outer tubes.
Temperature dependence of resonant Raman scattering in double-wall carbon nanotubes
Applied Physics Letters, 2003
The temperature-dependent frequency shift of resonant Raman spectra of double-wall carbon nanotubes is investigated in the range of 78 -650 K. We show here that different radial breathing mode ͑RBM͒ peaks, which are relative to different tube diameters, have a different temperature coefficient of frequency shift, and the larger diameter carbon nanotubes have more RBM frequency downshift with increasing temperature. We attribute the RBM frequency variation to the temperature dependence of the stretching force constant of C-C bond.
Diameter-selective resonant Raman scattering in double-wall carbon nanotubes
Physical Review B, 2002
Double-wall carbon nanotubes ͑DWNT's͒ have been studied by Raman scattering using different excitation wavelengths and their spectra compared to those of single wall nanotubes ͑SWNT's͒ and C 60 -SWNT peapods. Raman scattering from the radial and tangential vibrational modes of very small diameter dϳ0.6-0.9 nm secondary ͑interior͒ semiconducting tubes within the DWNT can be unambiguously identified with 647.1 and 1064 nm excitations. The frequency of the tangential displacement vibrational modes identified with these secondary ͑interior͒ tubes is found to be downshifted by ϳ7 cm Ϫ1 relative to that of the larger primary ͑exterior͒ tubes that exhibit a diameter dϳ1.3-1.6 nm. This downshift strongly suggests that at small tube diameters ͑i.e., dϳ0.7 nm), the associated wall curvature of the nanotube may require an admixture of sp 3 character in the C-C interaction. Our results also show that the value ␥ 0 ϭ2.90 eV for the nearest C-C tight binding integral is consistent with the resonant enhanced Raman scattering from DWNT's.